1. Field of the Invention
The present invention relates generally to measuring instruments for measuring voltages, temperature, pressure, sound intensity, illumination, or the like, and more particularly, to a instrumentation system using a common measuring meter in conjunction with a plurality of different sensor modules for allowing the common measuring meter to measure a wide variety of test parameters.
2. Description of the Prior Art
Electronic measuring instruments are commonly used to measure and display a wide variety of parameters, such as voltages, temperature, pressure, speed, frequency, acceleration, sound intensity, and illumination levels, to name a few. Such measuring instruments commonly include a sensor which generates an analog signal having a magnitude that varies in accordance with variations in the parameter being measured. While such analog signals can be used to directly drive analog display meters, it is now common to convert the analog signal, using an analog-to-digital converter, to a digital signal that can be displayed digitally on a display panel.
Assuming that an engineer or technician is required to measure a variety of different parameters, such person ordinarily requires a corresponding number of measuring instruments. However, the cost of maintaining a separate measuring instrument for each type of parameter to be measured can be significant.
In addition, many electronic measuring instruments in use position a gain amplifier between the sensor and the analog-to-digital converter. Often the gain amplifier must be calibrated for zero signal strength (offset adjustment) and full scale signal strength (gain adjustment) before reliable measurement readings can be taken.
Most electronic measuring instruments must be recalibrated periodically to ensure accurate measurements. A calibration lab will keep a log of the date each measuring instrument has been calibrated and the date on which calibration is next due. However, unless someone remembers to check the calibration log periodically, it sometimes happens that instruments continue to be used beyond the scheduled recalibration due date.
Different measuring instruments may have different degrees of accuracy depending upon the type of parameter being measured. Even among two or more instruments intended to measure the same parameter, the responsiveness and accuracy of the sensing elements of such instruments can vary widely. Yet, the digital displays associated with such instruments may display the resulting measurement in digital format using a greater number of digits than are actually significant digits within the accuracy of the particular sensing element being used.
Particular types of sensing elements can produce electrical signals representing the measured parameter that vary in different ways for a given change in the parameter being measured. For example, a temperature sensitive element might produce an electrical voltage that varies linearly with changes in the temperature being measured. In contrast, a pressure sensitive element might produce an electrical resistance that varies in accordance with a quadratic formula. Accordingly, for a measuring meter designed to be used with different types of sensors, it is advantageous to know the type of sensor that is in use at any particular time in order to determine the best algorithm for computing the measured value.
Accordingly, it is an object of the present invention to provide an instrumentation system that includes a measuring meter adapted to be used with a plurality of sensor modules for allowing the measuring meter to compute and display a variety of measured parameters.
Another object of the present invention is to provide such an instrumentation system which automatically calibrates the measuring meter depending upon the particular sensor module being used with the measuring meter.
Still another object of the present invention is to provide such an instrumentation system wherein the measuring meter displays a warning legend if the selected sensor module is due for calibration.
A further object of the present invention is to provide such an instrumentation system wherein the measuring meter can detect the type of sensor coupled thereto for determining the algorithm used to compute the measured value of the parameter being sensed by the sensor module.
Yet another object of the present invention is to provide such an instrumentation system wherein the measuring meter can detect the range of accuracy of the sensor coupled thereto for determining the number of significant digits to display when displaying the computed measured value.
These and other objects of the present invention will become more apparent to those skilled in the art as the description thereof proceeds.